DE2509612A1 - METHOD, DEVICE AND CORE FOR MANUFACTURING A LAMINATED HOLLOW BODY FROM THERMOPLASTIC MATERIAL - Google Patents

Description

15606/07 20 / H

NATIONAL CAN CORPORATION, Chicago, Illinois, USA

Method, device and core for production
a laminated hollow body made of thermoplastic material

The invention relates to a method, an apparatus and in particular a core for producing a laminated one Hollow body made of thermoplastic material, whereby in the process a coating is made by injection molding over a core thermoplastic material and the coating is then expanded by blow molding. The procedure is particularly aimed at the manufacture of hollow plastic objects and / or containers.

Recently, there has been proposed a method of manufacturing a bulkhead container, i.e., a semi-rigid plastic container provided with an inner liner or inner layer of a different material or another Materials. This inner shaft has different properties compared to the outer layer of the container. According to the known method, the preformed lining is in the form of a cover, for example after the Injection compression or thermal embossing technology

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is applied to a rod-shaped core and then a coating or preform is created around the liner in the injector of an injection blow blower. The liner provided coating is then expanded in the blow molding station of the injection blow moulder and then the lined container thus obtained is removed from the core in a product take-off station.

As a result of a pronounced tendency to wrinkle of the coating during the manufacture of the preform, which depends on the orientation and / or size fluctuations of the injection-embossed coating is based, can be found in many dividing wall containers produced in this way that the Lining is poorly fitted.

The object of the present invention is therefore to provide an improved method, a device for this and in particular to propose a core for carrying out the process for injection blow molding of a hollow plastic object, which overcomes the disadvantages of the prior art outlined above, i.e. wrinkling the coating is largely avoided. As a solution to this problem, the invention proposes on the basis of the above said method that a preformed layer of a second thermoplastic material over a porous core is placed and the pressure in the core is lowered below atmospheric pressure to form the layer of the second thermoplastic To hold material to the core prior to making the coating.

The device according to the invention is based on a device for injection blow molding of a laminated plastic

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Hollow body, with at least one blow mold core, an actuating device for transferring the blow mold core to various work stations of the device, a feed device for feeding and applying a layer to the blow mold core, including an injection device Tool for overmolding the blow mold core with plastic material in the form of a cover and with a blow molding device for inflating the cover to form the finished plastic hollow body. The invention consists in that the blow mold core is porous and can be evacuated from the inside.

In addition to solving the stated problem, the inventive Proposal has the advantage that the temperature conditions at the blow mold core are set and more uniform can be maintained and that prevents movements of the coating on the core during the implementation of the method will.

The blow mold core used in the process, which is, for example, rod-shaped, consists of a porous one Metal and in particular has a duct for the passage of air through a blow slot of the core as well as through the porous metal of the core head passes through, as will be explained in detail below. Through the blow mold core a reduction of the air pressure below atmospheric pressure in the core can be done while the coating is on the core is placed, i.e. during the actuation of the feeder, so that the coating on the core is opposite further movements is recorded until at least the onset of the preform injection molding process. Preferably however, the coating will continue to do so during the entire preform injection process held. In this way, the

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Temper the coating more evenly and reduce the tendency to wrinkle is reduced to a minimum during the injection molding of the preform due to the shrinking process.

Further advantages and features of the present invention emerge from the following description of a preferred one Embodiment based on the accompanying drawings as well as from further subclaims. In the drawings shows:

1 is a partially sectioned schematic plan view of a four-stage rotary injection blow molding machine;

Fig. 2 is a schematic section along the line 2-2 by the injection blow molding machine according to FIG. 1, and

3 shows a longitudinal section through a rod-shaped porous Blow mold core according to the present invention.

In order to facilitate a general understanding of the rotary injection blow molding machine in which the invention is embodied, reference is made to Figures 1 and 2, in which various system components of the machine are shown schematically. The rotatable injection blow molding machine, designated as a whole rait IO, consists essentially of a square index plate 12 which is mounted on a shaft 14. The shaft Ik is actuated by a motor and time control device designated as a whole by 16. This motor and time control device 16 includes the usual in-

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instruments, timing circuits, safety devices, etc. for the automatic and continuous operation of the Machine.

The machine iO contains four work stations, i.e. one feed station A for applying the liner, a preform injection station B, a blow molding station C and a product removal station D. The index plate 12 has a plurality of blow mold cores 18 and flow lines, which as a whole are denoted by 20 on. In addition, it includes intervening heat transfer lines that are not shown are.

The preform injection station B and the blow molding station C are provided with injection or blow molding tools, which are designated with 22 and 24 and which also have built-in heat supply lines. contained in a known manner. The latter are not shown.

In operation, the index plate 12 rotates intermittently further 90 ° by one cycle segment, namely after a time interval that is independent of the injection, blowing and removal time or the like. is. Be at the feeding station A. Linings 26 are removed from a corresponding magazine, generally designated 28, and placed on the blow mold cores 18 put on. After a certain time interval, the index plate 12 is rotated by 90 ° by the motor and time control device 16 rotated. It will be understood that simultaneously with the initiation of an index step (i.e. a rotating section in the cycle) open the preform injection molds 22 and the blow molds 24 and the index plate 12 from

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Reaching high is raised vertically in order to allow rotation of the index plate 12 at all. In general the lower mold halves are immobile, while the upper mold halves are mounted on vertically movable mold clamping plates, which are not shown. After the completion of the index step, the index plate 12 returns to its operating position in which the mold halves close over the mold cores 18.

At the preform injection molding station B, after a certain time interval, a hot material 30 in a plastic state is injected during a certain injection period through spray nozzles 32 around the mold cores 18 covered with the lining. This creates combined laminated preforms between the liner 26 and the molding surfaces 36 of the injection mold 22. ^{After a corresponding period of time, a further index step} is initiated in which the index plate 12 is rotated again by 90 ° so that the assembled preforms 34 can be brought into the tools of the blow molding station C. A pressure medium, generally compressed air, is introduced through the flow line 20 and the blow slots of the mold cores 18, thereby expanding the assembled preforms 34 and taking the shape of the molding surfaces 38 of the blow molds 24. Laminated containers 40 are thereby provided.

At the end of a subsequent period and others Index step, the index plate 12 is brought into a position in which the blow-molded container 40 at the product removal station D can be taken. The removal takes place, for example, by mechanical devices. the

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Containers are placed on a conveyor 42 for the following Inspection, filling, packaging and the like. It is understood that the sequence of operations explained above for a set of mandrels is correspondingly for each of the other blow mold cores applies and the described mode of operation of the four-stage rotatable injection blow molding machine is generally valid.

3 shows a mandrel 50 in the form of a rod, which consists essentially of a head 52 and a housing 54. The head 52 comprises a rod 56, a disk-shaped base plate 58, a tubular core pin 60: and a core pin carrier 62. The rod 56 is threaded at one end 6h and at the other end 66 centrally with the base plate 58, in the openings 68 are provided connected.

The tubular core pin 60 has a forwardly tapering inner wall 70 which is arranged around the cylindrical outer wall of the base plate 58 and extends coaxially with the rod 56 and away from it. The core pin 6o consists of two sections, namely a rear section 72 made of solid material, for example stainless steel, and a front section lh made of porous material, which has a large number of individual passages. The passages are incorporated, for example, during manufacture. The front section lh made of porous material

with fabric, for example, consists of one / two micron thick * stainless steel sheet. The rear section 72 is connected to the base plate 58.

* Pore-provided

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The core pin carrier 62 consists of a material with particularly good thermal conductivity properties, for example copper, and comprises a rear section 76 which is central to the base plate 58 and coaxially to the rod 56. The core pin support 62 also includes a helically shaped central portion 78 and an end portion 80. The screw of the helical intermediate portion 78 has flat thread crests which are in close contact with the tapered inner wall 70 of the core pin. The end section 80 of the core pin carrier 62 ends flush with the front section 1h of the core pin 60.

The housing 54 of the mold core consists of a cylindrical shaft 82 and a cylindrical sleeve section 8h and contains a central cylindrical bore 86. At the end of the shaft 82 facing away from the sleeve section 8h , two countersunk bores 88 and 90 are provided. The sleeve section 8h forms a cylindrical chamber 92 and has a shoulder surface 9h produced by a countersink. The rod 56 of the head 52 extends through the bore 86 and is urged by a spring 96 so that the head 52 is pulled against the shoulder surface Sh. For this purpose, a nut 98 is screwed onto the screw end 6h of the rod 56 and maintains a distance from the inner wall of the countersunk bore 90. The annular space between the rod 56 and the countersunk bores 88 and 90 or between the rod 56 and the bore 86 and the space between the rear portion of the core pin 60 and the inner surface of the cylindrical chamber 92 each serve as a passage for the pressure medium causing the blow molding.

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The head 52 is lifted from the housing ^ k in the direction of arrow A in FIG. 3 by a force device, not shown, which is assigned to the index plate 12 and presses on the nut 98, and thereby assumes the position shown in dashed lines. This creates a concentric passage for pressure medium between the head and the housing. By removing the lifting force, the head 52 returns to the stationary position under the action of the compressive force of the spring 96. In addition, gaseous medium passes through the openings (not shown in detail) in the porous metal of the front section Ik of the head 52, as will be explained in more detail below.

In operation, a number of mandrels 50 of FIG. 3 are as Blow molding cores 18 on the index plate 12 of the machine according to FIG 1 and 2 arranged. After a warm-up period, the machine's operating cycle runs after an index step has been completed by placing linings 26 on the mold cores 18 from the lining magazine through the feed device 28 are put on. The flow line 20 of the index plate 12 is in the feed station A via a line brought into connection with the suction side of a pump 102, so that at this station the pressure within the mold cores 18 descends and the liners are pressed tightly onto the surface of the mandrel 18. In this situation they will get through the negative pressure is maintained, which is maintained by a check valve when an index step is initiated. It goes without saying that when the connection between the flow line 20 and the line 100 is established, the flow line 20 is either connected to the suction side the pump 104, which runs continuously, or with a

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not shown vacuum accumulator, which is intermittently actuated pump is evacuated to negative pressure

is held. In the latter case, of course, appropriate pressure switches and the like are provided.

After completion of a cycle section, the index plate 12 is switched to the next station, i.e. to the spraying station B. At spray station B, hot molten plastic 30 is sprayed through spray nozzles 32 over the liners 26 is injected into the shaping space between the injection molding tools 22, so that the assembled preforms 34 are produced. In general, the liners 26 are adjusted to the temperature conditions prior to injecting the hot plastic for a certain period of time. It goes without saying that at the same time as the spraying process at spraying station B linings 26 are again placed on the mold cores 18 at the feed station A.

After rotating through a further cycle section, the assembled preforms 34 are inserted into the blow molds 2k at the blow station C. At this point, they now have an overall temperature sufficient for blow molding. When the flow line 20 is brought into connection with the pressure side of a pump 108 via a line 106, a device (not shown) pushes the check valve 104 out of the closed position. Compressed air now flows through the bore 86 and the outlet between the head 52 and the housing 5 ^; *, So that the composite preforms J) ¹ I expanded and pressed against the mold surfaces 38 of the blow mold 2k as explained above in connection with FIG. 3. This creates containers 40.

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After completion of the cycle section, the index plate 12

raised and indexed, the containers 40 produced reaching the product removal station D; there, the containers are ejected, for example by mechanical devices, and arrive on the conveyor k2 for subsequent treatment, for example inspection, filling or packaging. It will be understood that each side of the index plate 12 successively carries out the steps explained above, so that after each cycle section each set of mandrels on the index plate carries out one operation of the entire cycle.

As explained above, it allows the use of the porous mandrel according to the present invention, within the Molding core to maintain a vacuum during the application of the linings before and preferably also during the injection molding process and thereby preventing the liner from moving. This will cause the liner to wrinkle largely excluded. In addition, this makes the fit between the liner and mandrel less critical and wider tolerances can be allowed in the manufacture of the liners.

The inner design of the mold core enables a working medium to be introduced and passed through, e.g. hot air, during start-up of the injection blow molding device and likewise the introduction and passage of another working medium, e.g. ambient air, during the production cycle between the removal of the finished end product and the application of the linings.

The uniform passage of a working medium through the porous front section 74 of the core pin 72 is ensured by the

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helical turns and the flat spiral crests on the intermediate section 78 favored. The working medium flows evenly out of the surface of the front section 7k due to its porous design. It goes without saying that instead of the described helical design of the intermediate section 78, this section can also have a different shape, e.g. star-shaped in cross section, the pin carrier being axially aligned with the core pin and flat axially and radially directed outer surfaces as contact surfaces with the inner wall 70 of the core pin 6o owns. The flat spiral combs in the illustrated helical intermediate section 78 are advantageous because they form a sufficient contact and support surface for the core pin 60 and also promote the transfer of heat from the tip of the core pin 6o to the inner part of the pin carrier 62.

As mentioned above, the pin carrier 62 is preferably made of a material that conducts heat well, e.g. copper, in order to be able to dissipate heat, in particular from the end section 80. Because usually the tip, i.e. the end section 80 exposed to higher temperatures, which is due to the fact that the spray nozzles 32 for the hot plastic in the generally lie opposite the end section during the injection phase. For this reason it is preferable to be on the tip of the end portion 80 is also not provided with any porous metal.

As also already mentioned, the arrangement of the cores in the index plate 12 is chosen so that they have suitable Lines can be supplied with a cooling medium in order to keep the temperatures of the cores at certain values

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can and also other essential process parameters to be able to adjust.

The rear portion 72 of the core pin 60 is made of stainless steel to provide a more resistant contact surface between the head 52 and the housing 54 at the shoulder surface 9k and thereby extend the life of the mandrel over the condition in which the entire core pin 6O is made of porous Metal is made.

It goes without saying that the position of the blow slot in the mold core depends on the plastic composition of the respective preforms and their design depends. For example, in the case of polystyrene, the blow slot is located in the one shown in FIG. 3 position shown, while for polyolefin, for example, the blow slot is generally closer to the tip of the mandrel is arranged. Furthermore, it goes without saying that deviating from the arrangement of the mold core on a rotatable Injection blow molding machine with a plurality of mold cores these can be used in other processes and in conjunction with other injection blow molding machines, e.g. for devices with only one mandrel. It is also within the scope of the invention to make the mold core made of porous metal as an embossing element in vacuum thermal embossing and in a corresponding one Use the facility in which the liner is made, and then the mandrel in the Process explained here and the device used for this purpose for the production of, for example, partition-wall containers to use.

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Claims (1)

Patent (protection) claims 1Λ Process for the production of a laminated hollow body / made of thermoplastic material, in which a coating of thermoplastic material is created by injection molding over a core and the coating is then expanded by blow molding, characterized in that a preformed layer of a second thermoplastic material over a porous core and the pressure in the core is reduced to below atmospheric pressure in order to hold the layer of the second thermoplastic material on the core prior to the formation of the coating. 2. The method according to claim 1, characterized in that the negative pressure within the core during the injection molding process ganges is maintained, 3 · The method according to claim 1 or 2, characterized in that after pressure relief the provided with the coating Layer that forms a preform is expanded into the laminated hollow body by blow molding, k » Method according to one of claims 1 to 3, characterized in that the core is tempered before the layer is applied by passing a working medium through it, 5. Device for injection blow molding of a laminated plastic hollow body, with at least one blow mold core, one 509837/0678 Actuating device for transferring the blow mold core to different work stations of the device, a feed device for feeding and applying a layer to the blow mold core, including an injection device Tool for encapsulating the blow mold core with plastic material in the form of a coating and with a blow molding device to inflate the cover to the finished plastic hollow body, characterized in that the blow mold core (18) is porous and can be evacuated from the inside. 6. Apparatus according to claim 5 »characterized in that to maintain the vacuum in the blow mold core (18) the transfer of which to the injection device (B) is provided with a check valve (104). 7. Device according to claim 6, characterized in that the non-return valve (104) reduces the negative pressure up to the transfer of the blow mold core (18) to the blow molding station (C) maintains. 8. Device according to one of claims 5 to 7, characterized in that that a line for supplying a temperature control medium to the blow mold core (18) is provided. 9. Device according to one of Claims 5 to 8, characterized in that the check valve (104) is controllable. 10 · mold core for use in the device according to one of the Claims 5 to 9, characterized by a housing (54) 509837/0678 with a passage (86) for flow medium, a head (52) with a base plate (58) in which flow passages (68) are provided, and from a core pin (60) which is connected to the base plate (58) and through a flow connection between the passage (86) for flow medium in the Housing (5 ² O and the flow passages (68) in the base plate (58), as well as through a section (7 ² O of the core pin (60) made of porous metal. 11, mold core according to claim 10, characterized in that the base plate (58) is arranged displaceably in the housing (5 ² O. 12. Molding core according to claim 10 or 11, characterized in that the base plate (58) in the housing (5 ² O is under spring tension. 13. Mold core according to one of claims 10 to 12, characterized in that that the base plate (58) consists partially of a highly thermally conductive material, Ik, mold core according to one of Claims 10 to 13, characterized in that the base plate (58) has a pin carrier (62), the outer surface of which is partially helical and is in contact with the inner surface (70) of the core pin (60). 15 mold core according to one of claims 10 to 14, characterized in that that the front end (80) of the pin carrier (62) attached to the base plate (58) is flush with the End of the core pin (60) ends. 0 9 8 3 7/0678 Blank page